Catalyst and process for the epoxidation of olefinic compounds

Abstract: A catalyst composition having high epoxidation activity and resistant to leaching of its metal comprises molybdenum, vanadium, tungsten and/or titanium complexed to an organic or inorganic support through the intermediacy of an imidazole ligand. The catalyst may be used in epoxidation of olefinic compounds.

Description: This invention relates to a catalyst and process for the epoxidation of olefinic compounds. Epoxidation of olefinic compounds is a well known process which is operated industrially. For example the epoxidation of propylene to propylene oxide using alkyl hydroperoxide is known to be catalysed by a soluble molybdenum catalyst and by a heterogeneous titanium/silica catalyst. Sherrington and Simpson describe in Journal of Catalysis 131 115-126 (1991) polymer-supported molybdenum and vanadium cyclohexene epoxidation catalysts in which the metals are bound through a hydroxypropylated aminomethylpyridine ligand. US 4800188 discloses a catalyst composition comprising a transition metal complexed to a metalloporphyrin through a benzimidazole article. Such complexes may be used in the selective oxidation of alkanes, olefins and aromatic compounds and for epoxidation of cyclohexenes. However, there remains a need for an improved heterogeneous epoxidation catalyst. Thus, according to the present invention there is provided a catalyst composition comprising molybdenum, vanadium, tungsten and/or titanium complexed to an organic or inorganic support through the intermediacy of a pendent imidazole ligand. Also, according to the present invention there is provided a process for the epoxidation of olefinic compounds which process comprises reacting the olefinic compound with a peroxide in the presence of a catalyst composition comprising molybdenum, vanadium, tungsten and/or titanium complexed to an organic or inorganic support through the intermediacy of a pendent imidazole ligand. The present invention provides a novel catalyst which has high epoxidation activity and is resistant to leaching of its metal in use. The catalyst composition according to the present invention preferably comprises molybdenum, vanadium and/or tungsten, most preferably molybdenum. More than one metal may be present in the catalyst composition. The imidazole ligand may comprise unsubstituted imidazole or a substituted imidazole such as 2-pyridyl-2-imidazole, benzimidazole, 5-benzimidazole carboxylic acid and hydroxy substituted imidazoles and benzimidazoles. The imidazole ligand may be attached to the support through any part of the imidazole or substituted imidazole ligand provided that the imidazole ring is available for complexing to the metal of the catalyst. Suitably, the ligand loading in the catalyst composition is in the range 0.1 to 5 mmol g -1 preferably 0.25 to 2.5 mmol g -1 and the metal loading in the catalyst composition is suitably in the range 0.1 to 10 mmol g -1 preferably 0.1 to 5 mmol g -1 . Preferably, the ligand:metal molar ratio is in the range 1:1 to 15:1, more preferably 1:1 to 10:1. The organic support may be any suitable polymer and in particular one which is stable under the conditions of use of the catalyst composition. Suitable polymer supports comprise styrene polymers, methacryate polymers, glycidyl methacrylate polymers, benzimidazole polymers, polyimides, polybenzothiazoles, polybenzoxazoles and the like, optionally copolymers with suitable comonomers and optionally cross-linked. The support may comprise a functionalised inorganic support such as functionalised silica or alumina. Preferably the support comprises a polybenzimidazole. The catalyst composition according to the present invention may be prepared by effecting a ligand exchange reaction between an organometallic complex of molybdenum, vanadium, tungsten or titanium having a suitable leaving group with a support having imidazole ligands. Pendent imidazole ligands may be attached to a support by functionalisation of the support by methods known in the art. Thus for example, a styrene polymer with, for example, a reactive halide substituent may be reacted with a suitable nucleophile such as an amine-substituted imidazole to attach the imidazole to the styrene polymer support. Similarly, a lithiated polystyrene may be reacted with an electrophilic imidazole to attach the imidazole ligand to the polystyrene support. A polymer support comprising glycidyl methacrylate polymer may be reacted with either an electrophilic or nucleophilic imidazole to attach the imidazole ligand thereto. Where the support is inorganic such as silica that may be functionalised with chloromethyl pyridine by methods known in the art and thereafter reacted with an electrophilic imidazole. Suitable preparation procedures are described for example by Sherrington, DC and Hodge, P in "Polymer Supported Reactions in Organic Synthesis" J Wiley Chichester (1980). Polybenzimidazoles may be prepared by condensation of tetraamino compounds with diacids. See for example "Thermally Stable Polymers" by P E Cassidy and Marcel Dekker, New York (1980). In the process of the present invention the catalyst may be activated before use by oxidising it with a suitable peroxide. The catalyst may also be activated "in situ" by reaction with peroxide reactant. The olefinic compound for use in the process of the present invention may be any organic olefinic compound having at least one olefinic double bond. The olefinic compound may be straight-chain, branched-chain or cyclic. The olefinic compound may be acyclic, monocyclic, bicylic or polycyclic. The olefinic compound may be mono-olefinic, di-olefinic or polyolefinic. If more than one olefinic bond is present, the olefinic compound may be conjugated or non-conjugated. The olefinic compound may be substituted by an allylic hydroxyl, chloride, ether and/or ester group. The olefinic compound may be a vinyl ester, phenyl or nitrile compound. If substituted by electron-withdrawing groups for example nitrile, such groups should not be substituted directly on the olefinic double bond but should be remote therefrom. Preferably, any substituents are electron-donating. Preferably, the olefinic compound has the general formula (II): R - CH = CH - R' where R and R' are the same or different and are independently hydrogen; hydrocarbyl groups, for example alkyl, aryl, alkylaryl, cycloalkyl or alkylcycloalkyl groups; substituted hydrocarbyl groups or together from a cyclic hydrocarbyl or substituted hydrocarbyl group. Suitably R and R' each have less than 30 carbon atoms. R and R' may together form a cycloalkyl or alkylcycloalkyl group suitably having less than 10 carbon atoms. One or both of the R and R' may independently have allylic hydroxyl,chloride, ether and/or ester substituent groups. One or both of R and R' may independently have vinyl ester, nitrile and/or phenyl substituent groups, but having regard to the above comments on electron withdrawing substituents. Suitable olefinic compounds for use in the present invention may comprise one or more of ethylene, propylene, butenes, for example butene-1, cis or trans butene-2, pentenes, hexenes, octenes, decenes, cyclohexene, 4-vinyl-cyclohexene, unsaturated glycerin esters, allyl choride, styrene, methylene cyclohexane, cyclopentadiene and butadiene. A mixture of olefins may be used. The olefin may be used with minor amounts of impurities such as are known in the art, for example alkanes, aromatics, alcohols, ethers and acids but preferably, such impurities are inert to the reaction. In the process of the present invention the peroxide may be any suitable source of peroxide, for example hydrogen peroxide, an organic hydroperoxide for example an alkyl hydroperoxide, a peroxide ether or a peracid. Preferably the peroxide is tert-butyl hydroperoxide, cumene hydroperoxide, ethylbenzene hydroperoxide or hydrogen peroxide. The process of the present invention is particularly applicable to the epoxidation of propylene by tert-butyl hydroperoxide (TBHP) in the presence of low concentrations of tert-butyl alcohol (TBA); the TBHP and TBA being the product of isobutane oxidation and the TBA then being convertible to methyl tert-butyl ether (MTBE). The process of the present invention may be performed in neat liquid reagents or a solvent may be used such as an aromatic, aliphatic, alcohol, alkane, ester, ketone or halogenated solvent with solvents such as 1,2 dichloromethane and toluene being preferred over t-butanol and methanol. Water can only be tolerated in small quantities and is preferably absent. The process of the present invention may be performed at atmospheric or elevated pressure. Preferably, the process is performed at elevated pressure to maintain a suitable concentration of the olefinic compound in the liquid reaction medium if the olefinic compound is a gas at atmospheric pressure. A gas which is inert to the process such as nitrogen, helium, air or alkane may be used to maintain the elevated pressure. Suitably the operating pressure for the epoxidation of propylene is in the range atmospheric to 100 bar. The process of the present invention may be performed at any suitable temperature depending upon the reagents used. Preferably, the process of the present invention is performed at a temperature in the range 20 to 500°C. Catalysts according to the present invention comprising molybdenum complexed to polybenzimidazole have shown high temperature stability up to 400°C. The process of the present invention may be performed as a batch or as a continuous process, preferably as a continuous process. The molar ratio of peroxide to olefin may suitably be in the range 1:0.5 to 1:100 typically about 1:1 to 1:50. The molar ratio of catalyst to peroxide may be in the range 0.00001:1 to 1:1 typically about 0.002:1 to 0.03:1. The invention will now be illustrated with reference to the following examples. Preparation of catalyst composition (PBI. Mo catalyst Comparison Test 1 A catalyst composition not according to the present invention comprising molybdenum complexed to a polybenzimidole microporous resin (PBI. Mo) was prepared in the following procedure. 10g of wet polybenzimidizole microporous resin beads, AUROREZ (trade mark, Hoechst-Celanese) was stirred with 1N sodium hydroxide solution overnight, washed with deionised water until pH=7, washed with acetone and then dried in vacuo at 40°. The nitrogen content of the resin was then determined by microanalysis to be 15.15%, which, given that there are four nitrogen atoms in each polymer repeating unit, gives a repeating unit concentration of 2.71 mmolg -1 . The resin was then refluxed in toluene for 72 hours with molybdenum acetyl acetonate MoO 2 (acac) 2 at a molar ratio of organometallic complex:functional ligand of the resin of 2:1. Since for PBI there are two ligands per repeating unit, the ratio of organometallic complex: repeating unit of PBI was 4:1. The mother liquor turned blue. The resulting catalyst composition was then washed, with acetone using a Soxhlet extraction apparatus for approximately 48 hours. The resulting catalyst composition was dark blue with a few yellow beads dispersed throughout the resin. The molybdenum content of the catalyst composition was determined by grinding the material, treating with aqua regia and making up the resultant solution with water before analysis using atomic absorption spectroscopy. The catalyst composition was found to have a metal loading of 1.88 mmol g-1. (In another preparation the metal loading was 3.24 mmolg -1 ). In use, the amount of catalyst used was adjusted to give a constant metal concentration in the reaction mixture. The ligand loading for the PBI.Mo catalyst was calculated to be (1-weight molybdenum per gram) x ligand loading of the PBI resin = 2.22 molg -1 that is a ligand: metal ratio of 1.18:1. The catalyst composition was activated prior to use in some experiments by refluxing a weighed amount of catalyst (containing 0.06 mmol molybdenum) with 5 mmol tetra-butyl hydroperoxide (1.3-1.4 ml solution prepared as hereinafter described) in 25 ml 1,2 chloroethane for a predetermined period. During activation the catalyst composition turned a yellow colour. When not in use, the activated catalyst compositions were stored in 5 mmol tert-butyl hydroperoxide (1.3-1.4 ml solution) and 10 ml dichloroethane. The catalyst is not according to the present invention because the imidazole ligand comprises part of the support as opposed to being pendant thereto. It is included only for the purpose of comparison. Epoxidation of cyclohexene Epoxidation reactions were performed at 80°C using the molybdenum-loaded polybenzimidazole catalyst composition (PBI.Mo) previously prepared. The peroxide used in the Experiments was an anhydrous solution of tert-butyl hydroperoxide in toluene which was prepared by swirling (to avoid formation of an emulsion) together 65 ml tert-butyl hydroperoxide-70 and 80 ml toluene in a 200 ml separating funnel. The aqueous layer (15 ml) was discarded and the organic layer (130 ml) was refluxed in a 250 ml flask fitted with a Dean-Stark trap for approximately 1 hour, during which 4 ml water was collected and discarded. Then a drying tube was fitted and a further 4 ml of distillate removed through a side arm. The remaining anhydrous solution (122 ml) was cooled and stored for use over 4 A molecular sieve. The molarity of the tert-butyl hydroperoxide solution was determined by iodiometry. A 25 ml round-bottomed flask was used for the epoxidation reaction experiments, fitted with a reflux condenser and a water jacket connected to a temperature-controlled water recirculation bath to enable efficient and accurate temperature control. In a typical epoxidation reaction approximately 0.2g (0.06 mmmol molybdenum) of the catalyst composition (PBI.Mo), 8.4 ml of the olefin (0.083 mol cyclohexene). 0.2-0.3 ml 1,2 -dichloroethane and 0.5 ml bromobenzene (internal standard for the gas chromatographic analysis of the reaction product) were all placed in the reaction vessel and allowed to equilibrate thermally (80°C) for about 20 minutes. 5mmol tert-butyl hydroperoxide (1.3-1.4 ml solution) was then added and the reaction was monitored by periodically withdrawing 1 microlitre of the reaction mixture and injecting it onto a gas chromatograph to analyse the cyclohexene oxide concentration. A J&W Scientific DB-5 capillary column (30m, internal diameter 0.32mm, 1.0 micrometre thickness) was used with hydrogen carrier gas at 38 ml/min (40 kPa) and an oven temperature program of 100°C (1 minute) then increasing to 120°C at 40°C/minute. Each epoxidation was performed for a period of 4 hours. The yields of cyclohexene oxide were calculated as amount of cyclohexene oxide produced divided by the amount of tert-butyl hydroperoxide charged, expressed as a percentage. To determine the amount of metal leached from the resin during the course of the reaction, at the end of the reaction the catalyst composition was filtered off and washed thoroughly, together with the reaction vessel, with 1,2 dichloroethane, the reaction composition and combined washings being placed in a rotary evaporator to remove the solvent and leave a yellow residue. This residue was treated with aqua regia (15ml) for 48 hours before being diluted with water and analysed by atomic absorption spectroscopy. Comparison Test 2 The yields of cyclohexene oxide for reactions at 80°C using a catalyst composition which had not been activated and one which had been activated for 4 hours are given in Table 1. This is not an example according to the present invention because a catalyst not according to the present invention was employed. It is included only for the purpose of comparison. Comparison Test 2 Reaction Time (Minutes) Yield of cyclohexene oxide (%) Unactivated 4 hour Activated 20 60.6 79.6 40 92.3 92.2 60 97.1 96.0 80 98.8 97.0 100 100 98.0 120 99.9 97.8 180 98.7 99.5 240 98.3 99.2 Example 1 - Preparation of Catalyst Composition Having Molybdenum supported by Pendent Imidazole Ligands on Organic Polymer Supports Catalyst composition having molybdenum supported by pendent imidazole ligands on organic polymers, polystryrene (Ps) and polylglycidyl methacrylate (PGMA) were prepared by the following procedures: (a) Preparation of Macroreticular Chloromethylated Polystyrene This functionalised resin was prepared by the suspension copolymerisation of vinylbenzene chloride and divinylbenzene as follows: Synthesis of stabilising solution (or bulk phase): 9g boric acid was dissolved in 378ml deionised H 2 O and aqueous cellosize solution (12g, 0.17% w/v) added. The pH of the solution was adjusted to 10.3 using 50% aqueous NaOH solution. Xanthan gum solution (300ml, 0.3% w/v) was added along with NaCl (120g). The resulting solution was stirred in a 1 litre suspension polymerisation reactor at a temperature of 80°C for a period of 1 hour prior to the addition of the monomer/diluent solution. Monomer/diluent solution: 60ml vinylbenzene chloride, 40ml divinylbenzene and 50ml 2-ethylhexanol stirred in flask. AIBN initiator added (1g) and solution stirred until AIBN dissolved. The solution was slowly added to the stirred bulk phase dropwise using an addition funnel. The resulting polymerisation mixture was left for a period of 5 hours at a temperature of 80°. Upon completion, the resulting beads were filtered off using a 100µm sieve, washed thoroughly with water and acetone, and extracted with acetone in a Soxhlet apparatus for a period of 24 hours before being dried in vacuo at 40°C. The functionalised resin was used in the preparation of organic polymer supports having pendent imidazole ligands. (b) Preparation of Poly(glycidyl methacrylate) PGMA Macroreticular poly(glycidyl methacrylate) crosslinked with 40% ethylene glycol dimethylacrylate was synthesised by suspension polymerisation of a mixture of glycidyl methacrylate and ethylene glycol dimethacrylate (6/4 vol/vol) with a mixture of cyclohexanol and dodecanol (9/1 vol/vol) as the porogen (monomer-diluent, 1/1 vol/vol). Biozan Gum R was used as stabiliser and a resin having a particle size of 300-800µm was obtained. This procedure is described by D.Lindsay and D.C.Sherrington in Reactive Polymers 1985 3 , 327-339. This resin was used in the preparation of organic polymer supports having pendent imidazole ligands. (c) Preparation of 2-pyridyl-2-imidazole ligand This ligand was synthesised according to the procedure in South Africa Patent 77/5398 as follows: Ice-cold solutions of 2-pyridine carboxaldehyde (78ml, 0.79mol), glyoxal (120ml) and ethanol (100ml) were mixed in a 3-necked, 1 litre round-bottom flask under a nitrogen atmosphere. Concentrated ammonia solution (120ml, 2.16mol) was added, and the flask maintained at 0°C for 30 minutes with continuous stirring, until the initial vigorous reaction died down. The flask was stoppered, retaining the nitrogen atmosphere, and stirred at room temperature for 3 hours. Excess ethanol (approx. 100ml) was removed and the remaining dark brown liquid extracted with 200ml portions of ether 10 times. The ether extracts were dried with magnesium sulphate prior to the ether being removed by evaporation to yield a brown solid, which was recrystallised using ethyl acetate. This imidazole ligand was used in the preparation of organic polymer supports having pendent imidazole ligands. (d) Functionalisation of macroreticular chloromethylated polystyrene and poly (glycidyl methacrylate) resins with imidazole ligands. The chloromethylated polystyrene (Ps) and poly (glycidyl methacrylate) (PGMA) resins were functionalised with the following imidazole ligands imidazole (Im), benzimidazole (BzIm), 2-pyridyl-2-imidazole (PyIm) and 5-benzimidazole carboxylic acid (5BzCOOH) as follows: Chloromethylated polystyrene. (Ps) Ps resin (5g, 0.021 mol -CH 2 Cl) was refluxed with the ligand (0.063 mol, 3:1 ligand: -CH 2 Cl) in toluene (120ml) for a period of 12 hours. The resultant support was extracted with acetone in a Soxhlet apparatus for 24 hours and dried in vacuo at 40°C. Poly (glycidyl methacrylate). PGMA resin (5g, 0.020 mol epoxide group) was refluxed with the ligand (0.040 mol, 2:1 ligand: epoxide group) in toluene (120ml) for a period of 12 hours. The resultant support was extracted with acetone in a Soxhlet apparatus for 24 hours and dried in vacuo at 40°C. (e) Attachment of 5-benzimidazole carboxylic acid (5BzCOOH) to chloromethylated polystyrene (Ps) 5-Benzimidazole carboxylic acid (6.804g, 0.042 mol) and NaOH (1.68g, 0.042 mol) (1:1 molar ratio employed in order to ensure deprotonation of carboxylic acid group only) were stirred in 150ml ethanol for 4 hours in a flask fitted with a drying tube. Ps resin (5g, 0.021 mol -CH 2 Cl) was added and mixture refluxed for 24 hours. The resultant support was extracted with acetone in Soxhlet apparatus for 48 hours and dried in vacuo at 40°C. (f) Polymer Supports. Microanalytical, ligand loading and IR data for the functionalised polymer supports are given in Table 2. Elemental microanalysis, ligand loading and IR data for functionalised polymer support resins. Resin % Ligand Loading (mmol g -1 ) IR C H N Ps.Im 74.8 6.8 3.6 1.30 1260 cm -1 loss of -CH 2 Clwag 1550 cm -1 C=N str. Ps.BzIm 72.8 6.9 3.8 1.34 750 cm -1 arom. ring str. Ps.PyIm 71.2 5.9 9.2 2.19 1450 cm -1 C=N str. Ps.5BzCOOH 74.8 6.3 1.8 0.42 3440 cm -1 N-H str. 1590 cm -1 C=O str. PGMA.Im 54.0 6.8 5.7 2.04 3400 cm -1 OH str. 1550 cm -1 C=N str. PGMA.BzIm 57.0 6.3 4.7 1.67 750 cm -1 arom. ring str. PGMA.PyIM 56.0 6.3 4.5 1.06 1450 cm -1 C=N str. (g) Preparation of Catalyst Compositions Catalyst compositions were prepared by refluxing the organic polymer support with a 2:1 molar excess of metal acetylacetonate before being washed with acetone in a Soxhlet apparatus. During the preparation of all the supported Mo catalyst compositions it was noted that the colour of the reaction solution turned dark blue in all cases. This colour was also detected in the initial extraction solvent in the Soxhlet apparatus but disappeared after the introduction of fresh solvent. IR spectra of all the supported complexes were recorded, and salient data from these, along with the colours of the complexes, are listed in Table 3. Metal and ligand loadings are given in Table 4. IR Data for Molybdenum supported on organic polymer supports. Complex Colour IR (cm -1 ) Mo=O str. Mo-O-Mo str. Ps.Im.Mo Brown 960 910 - Ps.BzIm.Mo Green 956 910 - Ps.PyIm.Mo Brown 960 915 - Ps.5BzCOO.Mo Green 960 904 - PGMA.Im.Mo Green 957 906 - PGMA.BzIm.Mo Green 953 916 - PGMA.PyIm.Mo Green 946 910 - PBI.Mo Dark Blue 950 979 - Metal Loading Data for molybdenum supported on organic polymer supports Complex Metal Loading Ligand Loading (mmol g -1 ) Ligand: Metal Ion Ratio (mmol g -1 ) (g g -1 ) Ps.Im.Mo 0.77 0.074 1.20 1.56 : 1 Ps.BzIm.Mo 0.93 0.089 1.22 1.31 : 1 Ps.PyIm.Mo 0.47 0.045 2.09 4.45 : 1 Ps.5BzCOO.Mo 0.19 0.019 0.41 2.16 : 1 PGMA.Im.Mo 0.46 0.094 1.95 4.26: 1 PGMA.BzIm.Mo 0.20 0.019 1.64 8.27 : 1 PGMA.PyIm.Mo 0.66 0.063 0.99 1.49 : 1 When required, the polymer-supported molybdenum was subjected to an activation procedure prior to use in an epoxidation. An exact weight (containing 0.06mmol Mo) of each complex was refluxed for a known period with TBHP (5mmol, 1.3-1.4ml) in 1,2 dichloroethane (25ml). When not in use in an epoxidation, the activated catalyst was stored in TBHP (5mmol, 1.3-1.4ml) and 1,2 dichloroethane (10ml). During the activation process the colour of all the complexes changed to yellow without exception. A catalyst according to the present invention having pendent 2-pyridyl imidazole ligands was prepared as above described and had a repeating unit represented by the general formula (I): wherein P ○ represents a macroreticular polystyrene backbone. The catalyst thus prepared having repeating units represented by general formula (I) was designated PsPyImMo and had 2.09 mmol ligand g -1 and 0.47 mmol Mo g -1 . A catalyst according to the present invention having pendent benzimidazole ligands was prepared as described above and had repeating unit represented by the general formula (II): wherein P ○ represents a macroreticular polystyrene backbone. The catalyst having repeating units represented by general formula (II) was designated Ps5BzCOOMo and had 0.41 mmol ligand g -1 and 0.19 mmole Mo g -1 . Example 2 - Epoxidation of Cyclohexene Comparison Test 2 was repeated using the catalyst compositions prepared in Comparison Test 1. The results are given in Table 5, together with the results from Comparison Test 2. Yields were based on tertbutyl hydroperoxide conversion. Reaction conditions were 0.5 mmol of tertbutyl hydroperoxide, 83 mmol of cyclohexene, 0.06 mmol of catalyst and 80°C temperature. Epoxidations of Cyclohexene Catalyst Activation Conditions Cyclohexene Oxide Yield (%) 20 min 60 min 240 min PBI. Mo Unact. 60.6 97.1 98.3 4hr act. 79.6 96.0 99.2 Ps. Im. Mo Unact. 1.9 3.1 24.0 4hr act. 14.9 20.0 95.7 Ps. BzIm. Mo Unact 1.9 3.1 24.0 4hr act. 14.5 20.7 87.8 Ps. PyIm. Mo Unact. 19.6 26.4 87.8 4hr act. 6.7 9.3 74.1 Ps. 5BzCOO. Mo Unact. 3.4 23.8 100.0 4hr act. 11.6 41.5 100.0 PGMA. Im. Mo Unact. 4.5 22.8 83.6 4hr act. 10.0 29.0 92.0 PGMA. BzIm. Mo Unact. 17.2 37.4 60.7 4hr act. 21.4 52.9 89.5 PGMA. PyIm.Mo Unact. 53.9 84.9 100.0 4hr act. 42.3 87.6 100.0 Example 3 - Epoxidation of Propene Using PsPyImMo Catalyst PsPyImMo catalyst prepared in Example 1 was used as catalyst for the epoxidation of propene using t-butylhydroperoxide. The reaction conditions were 10 mmol t-butylhydroperoxide, 0.12 mmol molybdenum in the catalyst, 238 mmol propene; temperature 80°C and pressure 400 psi (using helium). The catalyst was used and reused in a series of epoxidation runs each of 1 hour. The catalyst was activated for 4 hours as previously described prior to the initial epoxidation run. The results, shown in Table 6 show the catalyst to have high activity and selectivity for propene epoxidation. There was no molybdenum leaching. Turnover frequency (TOF) is the moles of product produced per unit time divided by moles of active catalyst, which as metal leaching is negligible is approximately moles of product produced per unit time divided by moles of metal originally present. 50% TOF was calculated as 50% of material converted/time taken, per mol. Mo used in catalyst. Catalyst recycling experiments - epoxidation of propene using Ps.PyIm.Mo catalyst Example 3 Run Propylene Oxide Yield (%) Mo Leached % Turnover Frequency (mol epoxide min -1 mol Mo -1 ) 1 98.9 0 1.37 2 95.3 0 1.32 3 97.7 0 1.36 4 - 0 - 5 95.0 0 1.32 6 - 0 - 7 93.4 0 1.30 8 92.8 0 1.29 9 92.8 0 1.29 10 - 0 - "-" = data were not obtained. Example 4 - Epoxidation of Propene Using Ps5BzCOOMo Catalyst Example 3 was repeated using Ps5BzCOOMo catalyst prepared in Example 1. The catalyst was not activated prior to the initial epoxidation run. The results shown in Table 7 show the catalyst to have high activity and selectivity for propene epoxidation. The molybdenum leaching was negligible. Catalyst recycling experiments - epoxidation of propene using Ps5BzCOOMo catalyst Example 4 Run Propylene Oxide Yield (%) Mo Leached (%) Turnover Frequency (mol epoxide min -1 mol Mo -1 ) 1 100.0 1.1 1.39 2 88.0 1.1 1.22 3 87.4 1.1 1.21 4 - 0 - 5 86.5 0 1.20 6 84.9 0 1.18 7 85.5 0 1.19 8 86.5 0 1.20 9 86.2 0 1.20 10 88.2 0 1.20 "-" = data were not obtained. Example 5 - Epoxidation of Propene Using PGMA PyIm.Mo Catalyst Example 3 was repeated using PGMA.PyIm.Mo prepared in Example 1 which was not activated prior to the initial epoxidation. The results are shown in Table 8. Catalyst recycling experiments - Epoxidation of propene using PGMA.PyIm.Mo catalyst. Run Propylene Oxide Yield (%) Mo Leached (%) Turnover Frequency (mol epoxide min -1 mol Mo -1 ) 1 90.1 1.1 1.25 2 89.3 1.1 1.24 3 74.1 0 1.03 4 - 0 - 5 43.4 0 0.60 6 53.6 0 0.74 7 - 0 - 8 55.4 0 0.77 9 53.8 0 0.75 10 53.9 0 0.75 Comparison Test 3 - Epoxidation of propene using PGMA.AMP.Mo Catalyst Example 3 was repeated using a catalyst comprising molybdenum supported on polyglycidyl methacrate functionalised with 2-aminomethyl pyridine. PGMA.AMP.Mo which had been activated for 4 hours before use. This is not an example according to the present invention. The results for 1 hour reaction twice are shown in Table 9. Catalyst recycling experiments - Epoxidation of propene using PGMA.AMP.Mo catalyst. Run Propylene Oxide Yield (%) Mo Leached (%) Turnover Frequency (mol epoxide min -1 mol Mo -1 ) 1 84.5 0.7 1.17 2 82.8 0.7 1.15 3 94.8 0.7 1.32 4 88.6 0.7 1.23 5 96.6 0.7 1.34 6 93.6 0.7 1.30 7 99.0 2.1 1.38 8 83.9 0.7 1.17 9 82.0 0 1.14 10 81.7 0 1.13

Claims: A catalyst composition comprising molybdenum, vanadium, tungsten and/or titanium complexed to an organic or inorganic support through the intermediacy of a pendent imidazole ligand. A catalyst composition as claimed in claim 1 in which the imidazole ligand comprises unsubstituted imidazole, 2-pyridyl imidazole benzimidazole, hydroxsubstituted imidazole, hydroxy-substituted benzimidazole or 5-benzimidazole carboxylic acid. A catalyst composition as claimed in claim 2 in which the support comprises an organic polymer. A catalyst composition as claimed in claim 3 in which the polymer support comprises a styrene polymer or a glycidyl methacrylate polymer. A catalyst composition as claimed in claim 4 in which the imidazole ligand comprises imidazole, 2-pyridyl imidazole, benzimidazole or 5-benzimidazole carboxylic acid. A catalyst composition as claimed in claim 1 comprising molybdenum complexed to a polymer support comprising poly[2,2'(m-phenylene)-5,5'-benzimidazole]. A process for the epoxidation of an olefinic compound with a peroxide which process comprises reacting the olefinic compound with a peroxide in the presence of a catalyst composition as claimed in any one of claims 1 to 6. A process as claimed in claim 7 in which the olefinic compound has the general formula (II) : R - CH = CH - R' wherein R and R' are the same or different and are independently hydrogen;hydrocarbyl groups; substituted hydrocarbyl groups; or together form a cyclic hydrocarbyl or substituted hydrocarbyl group. A process as claimed in claim 8 in which the R and R' groups are independently alkyl, aryl, alkylaryl, cycloalkyl or alkylcycloalkyl groups each having less than 30 carbon atoms, or together form a cyclcoalkyl or alkylcycloalkyl group having less than 10 carbon atoms. A process as claimed in claim 8 in which the one or both of the R and R' groups independently have allylic hydroxyl, chloride, ether and/or ester substituent groups, or vinyl ester, nitrile and/or phenyl substituent groups with the proviso that electron-withdrawing substitutent groups are not substituted directly on the olefinic double bond. A process as claimed in claim 8 in which the olefinic compound comprises at least one compound selected from the group consisting of ethylene, propylene, butenes, pentenes, hexenes, octenes, decenes, cyclohexene, unsaturated glycerin esters, allyl chloride, styrene, 4-vinyl cyclohexene, methylene cyclohexane, allyl chloride, cyclopentadiene and butadiene. A process as claimed in claim 11 in which the olefinic compound comprises propylene, oct-1-ene, cyclohexene, styrene, 4-vinyl cyclohexene, methylene cyclohexane or allyl chloride. A process as claimed in any one of claims 7 to 12 in which the peroxide comprises hydrogen peroxide, an organic hydroperoxide, a peroxide ether or a peracid. A process as claimed in claim 13 in which the peroxide comprises tert-butyl hydroperoxide, cumene hydroperoxide, ethylbenzene hydroperoxide or hydrogen peroxide. A process as claimed in claim 14 in which the olefinic compound comprises propylene and the peroxide comprises tert-butyl hydroperoxide, optionally in the presence of tert-butyl alcohol.

Inventors: CUNNINGTON MALCOLM JOHN, MILLER MATTHEW MORE, OLASON GUNNAR UNIVERSITY OF ST, SHERRINGTON DAVID C UNIVERSITY, SIMPSON SYDNEY, CUNNINGTON, MALCOLM JOHN, MILLER, MATTHEW MORE, OLASON, GUNNAR, UNIVERSITY OF STRATHCLYDE, SHERRINGTON, DAVID C., UNIVERSITY OF STRATHCLYDE, SIMPSON, SYDNEY
Applicants: BP CHEM INT LTD, BP CHEMICALS LIMITED
Application year: 1994
Main classification: B01J31
IPC codes: C07D303, B01J31, C07D301, C07B61